1. Field of the Invention
This invention relates to a series connection apparatus for generators and a single-phase three-wire output apparatus for a generator.
2. Description of the Related Art
There is known a generator, e.g., an engine generator equipped with an inverter that once converts alternating current outputted by an engine-driven generator unit to direct current and then converts the direct current into alternating current of a predetermined frequency (utility frequency) by driving switching elements with a PWM signal generated using a reference sine wave of a desired output voltage waveform and a carrier. Also a technique to connect two such the engine generators for parallel running is known, as taught by Japanese Laid-Open Patent Application No. Hei 8 (1996)-205543.
When the two generators are connected in parallel (or in series) as taught in the publication, it is necessary to conduct phase synchronous operation for synchronizing phases of alternating current outputs and, since inputting an output of one of the two generators through a signal line may cause short circuit, an additional communication line is required.